// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2006-2008 Benoit Jacob <jacob.benoit.1@gmail.com>
// Copyright (C) 2009 Ricard Marxer <email@ricardmarxer.com>
// Copyright (C) 2009-2010 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_REVERSE_H
#define EIGEN_REVERSE_H

namespace Eigen {

namespace internal {

    template <typename MatrixType, int Direction> struct traits<Reverse<MatrixType, Direction>> : traits<MatrixType>
    {
        typedef typename MatrixType::Scalar Scalar;
        typedef typename traits<MatrixType>::StorageKind StorageKind;
        typedef typename traits<MatrixType>::XprKind XprKind;
        typedef typename ref_selector<MatrixType>::type MatrixTypeNested;
        typedef typename remove_reference<MatrixTypeNested>::type _MatrixTypeNested;
        enum
        {
            RowsAtCompileTime = MatrixType::RowsAtCompileTime,
            ColsAtCompileTime = MatrixType::ColsAtCompileTime,
            MaxRowsAtCompileTime = MatrixType::MaxRowsAtCompileTime,
            MaxColsAtCompileTime = MatrixType::MaxColsAtCompileTime,
            Flags = _MatrixTypeNested::Flags & (RowMajorBit | LvalueBit)
        };
    };

    template <typename PacketType, bool ReversePacket> struct reverse_packet_cond
    {
        static inline PacketType run(const PacketType& x) { return preverse(x); }
    };

    template <typename PacketType> struct reverse_packet_cond<PacketType, false>
    {
        static inline PacketType run(const PacketType& x) { return x; }
    };

}  // end namespace internal

/** \class Reverse
  * \ingroup Core_Module
  *
  * \brief Expression of the reverse of a vector or matrix
  *
  * \tparam MatrixType the type of the object of which we are taking the reverse
  * \tparam Direction defines the direction of the reverse operation, can be Vertical, Horizontal, or BothDirections
  *
  * This class represents an expression of the reverse of a vector.
  * It is the return type of MatrixBase::reverse() and VectorwiseOp::reverse()
  * and most of the time this is the only way it is used.
  *
  * \sa MatrixBase::reverse(), VectorwiseOp::reverse()
  */
template <typename MatrixType, int Direction> class Reverse : public internal::dense_xpr_base<Reverse<MatrixType, Direction>>::type
{
public:
    typedef typename internal::dense_xpr_base<Reverse>::type Base;
    EIGEN_DENSE_PUBLIC_INTERFACE(Reverse)
    typedef typename internal::remove_all<MatrixType>::type NestedExpression;
    using Base::IsRowMajor;

protected:
    enum
    {
        PacketSize = internal::packet_traits<Scalar>::size,
        IsColMajor = !IsRowMajor,
        ReverseRow = (Direction == Vertical) || (Direction == BothDirections),
        ReverseCol = (Direction == Horizontal) || (Direction == BothDirections),
        OffsetRow = ReverseRow && IsColMajor ? PacketSize : 1,
        OffsetCol = ReverseCol && IsRowMajor ? PacketSize : 1,
        ReversePacket = (Direction == BothDirections) || ((Direction == Vertical) && IsColMajor) || ((Direction == Horizontal) && IsRowMajor)
    };
    typedef internal::reverse_packet_cond<PacketScalar, ReversePacket> reverse_packet;

public:
    EIGEN_DEVICE_FUNC explicit inline Reverse(const MatrixType& matrix) : m_matrix(matrix) {}

    EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Reverse)

    EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index rows() const EIGEN_NOEXCEPT { return m_matrix.rows(); }
    EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index cols() const EIGEN_NOEXCEPT { return m_matrix.cols(); }

    EIGEN_DEVICE_FUNC inline Index innerStride() const { return -m_matrix.innerStride(); }

    EIGEN_DEVICE_FUNC const typename internal::remove_all<typename MatrixType::Nested>::type& nestedExpression() const { return m_matrix; }

protected:
    typename MatrixType::Nested m_matrix;
};

/** \returns an expression of the reverse of *this.
  *
  * Example: \include MatrixBase_reverse.cpp
  * Output: \verbinclude MatrixBase_reverse.out
  *
  */
template <typename Derived> EIGEN_DEVICE_FUNC inline typename DenseBase<Derived>::ReverseReturnType DenseBase<Derived>::reverse()
{
    return ReverseReturnType(derived());
}

//reverse const overload moved DenseBase.h due to a CUDA compiler bug

/** This is the "in place" version of reverse: it reverses \c *this.
  *
  * In most cases it is probably better to simply use the reversed expression
  * of a matrix. However, when reversing the matrix data itself is really needed,
  * then this "in-place" version is probably the right choice because it provides
  * the following additional benefits:
  *  - less error prone: doing the same operation with .reverse() requires special care:
  *    \code m = m.reverse().eval(); \endcode
  *  - this API enables reverse operations without the need for a temporary
  *  - it allows future optimizations (cache friendliness, etc.)
  *
  * \sa VectorwiseOp::reverseInPlace(), reverse() */
template <typename Derived> EIGEN_DEVICE_FUNC inline void DenseBase<Derived>::reverseInPlace()
{
    if (cols() > rows())
    {
        Index half = cols() / 2;
        leftCols(half).swap(rightCols(half).reverse());
        if ((cols() % 2) == 1)
        {
            Index half2 = rows() / 2;
            col(half).head(half2).swap(col(half).tail(half2).reverse());
        }
    }
    else
    {
        Index half = rows() / 2;
        topRows(half).swap(bottomRows(half).reverse());
        if ((rows() % 2) == 1)
        {
            Index half2 = cols() / 2;
            row(half).head(half2).swap(row(half).tail(half2).reverse());
        }
    }
}

namespace internal {

    template <int Direction> struct vectorwise_reverse_inplace_impl;

    template <> struct vectorwise_reverse_inplace_impl<Vertical>
    {
        template <typename ExpressionType> static void run(ExpressionType& xpr)
        {
            const int HalfAtCompileTime = ExpressionType::RowsAtCompileTime == Dynamic ? Dynamic : ExpressionType::RowsAtCompileTime / 2;
            Index half = xpr.rows() / 2;
            xpr.topRows(fix<HalfAtCompileTime>(half)).swap(xpr.bottomRows(fix<HalfAtCompileTime>(half)).colwise().reverse());
        }
    };

    template <> struct vectorwise_reverse_inplace_impl<Horizontal>
    {
        template <typename ExpressionType> static void run(ExpressionType& xpr)
        {
            const int HalfAtCompileTime = ExpressionType::ColsAtCompileTime == Dynamic ? Dynamic : ExpressionType::ColsAtCompileTime / 2;
            Index half = xpr.cols() / 2;
            xpr.leftCols(fix<HalfAtCompileTime>(half)).swap(xpr.rightCols(fix<HalfAtCompileTime>(half)).rowwise().reverse());
        }
    };

}  // end namespace internal

/** This is the "in place" version of VectorwiseOp::reverse: it reverses each column or row of \c *this.
  *
  * In most cases it is probably better to simply use the reversed expression
  * of a matrix. However, when reversing the matrix data itself is really needed,
  * then this "in-place" version is probably the right choice because it provides
  * the following additional benefits:
  *  - less error prone: doing the same operation with .reverse() requires special care:
  *    \code m = m.reverse().eval(); \endcode
  *  - this API enables reverse operations without the need for a temporary
  *
  * \sa DenseBase::reverseInPlace(), reverse() */
template <typename ExpressionType, int Direction> EIGEN_DEVICE_FUNC void VectorwiseOp<ExpressionType, Direction>::reverseInPlace()
{
    internal::vectorwise_reverse_inplace_impl<Direction>::run(m_matrix);
}

}  // end namespace Eigen

#endif  // EIGEN_REVERSE_H
